1. Field of the Invention
The present invention relates to a heat exchanger, and more particularly, to a refrigerant leak-preventive structure in a heat exchanger of a refrigerator, in which refrigerant pressurized by a compressor to a high temperature and high pressure or a low temperature and low pressure flows. The refrigerant leak-prevention structure prevents leakage of refrigerant and introduction of external air both of which are generated at bonded sections between refrigerant tubes and headers. However, the heat exchanger of the invention is not restricted only to the refrigerator.
2. Description of the Related Art
A refrigerator includes a compressor, a condenser, a throttle valve and an evaporator all of which constitute a system operation in the order named. In the refrigerator, heat is absorbed in the evaporator while more heat is discharged out of the refrigerator via the condenser. In particular, the condenser and the evaporator function as a heat exchanger by absorbing and discharging heat.
The conventional heat exchanger performs heat exchange of refrigerant with a pair of metal refrigerant tubes for introducing or discharging refrigerant, headers fixed to both ends of the metal refrigerant tubes and a plurality of fins formed in outer peripheries of the metal refrigerant tubes. In particular, the fins and the refrigerant tubes are coupled by using expansion of the refrigerant tubes and thus typically have a predetermined gap between the metal bodies.
Owing to the metal structure, however, the conventional heat exchanger made of metal has a problem in that noises are generated at contact points between the metal bodies in on/off operation of the refrigerator, thereby causing inconvenience to the user. In order to improve this problem, a plastic heat exchanger is generally used at present.
FIG. 1 illustrates a conventional plastic heat exchanger in the form of a tri-tube heat exchanger having an integral structure of a fin, a refrigerant tube and a defrosting tube.
Referring to FIG. 1, the conventional plastic heat exchanger 112 includes a refrigerant tube, a fin and tube group or fin-tubes group 118 which is defined by combining a number of fins and defrosting tubes, fin-tubes group headers or headers 120 disposed at both ends of the fin-tubes group 118, right and left header tanks 124 and 126 extended from the headers 120. In particular, the fin-tubes group 118 indicates an array of ducts, in which at least a refrigerant tube and fins are integrally formed in each duct.
A method of fabricating the above plastic heat exchanger, in particular, for bonding the fin-tubes group 118 and the headers 120 has been disclosed in U.S. patent application Ser. No. 09/954,056, which will be briefly described as follows.
The undesignated reference numbers 130 and 132 indicate an inlet tube and an outlet tube of refrigerant, respectively.
FIG. 2 illustrates a process of combining the fin-tubes group 118 and the headers 120.
Referring to FIG. 2, the process of combining the fin-tubes group 118 and the headers 120 includes: primarily forming plastic into the fin-tubes group 118; double extruding at both ends of the plastic fin-tubes group 118 to form the headers 120; and placing thermal fusion jigs 136 into interspaces of the plastic headers 120 in a supporting fashion and thermal pressing an upper central portion of the fin-tubes group 118 using a thermal fusion apparatus 128 having thermal fusion molds 134 to thermal fuse the fin-tubes group 118 and the headers 120 more strongly.
In particular, the thermal fusion molds 134 are in the shape of an overturned triangle so that ends of the fin-tubes group 118 are flared strongly bonding to the header 120. The non-described numeral 140 indicates power lines.
The headers 120 are thermal fused to both ends of the fin-tubes group 118 according to the above fusion process, thereby possibly preventing abnormal noise from occurring in on/off operation of a refrigerator which has been a problem in the conventional heat exchanger made of metal.
In particular, since the fin-tubes group 118 is bonded to the header 120 via thermal fusion, there are advantages in that the plastic heat exchanger 112 is readily fabricated and the manufacturing cost thereof can be reduced.
Where the conventional heat exchanger 112 constructed according to the above bonding process is utilized as an evaporator, refrigerant is introduced under an atmospheric pressure (e.g., 0.9 to 1 atm.) similar to the atmospheric pressure and thus refrigerant leak or introduction owing to differential pressure may not take place.
However, where the conventional heat exchanger 112 is utilized as a condenser, refrigerant having a high temperature and pressure (e.g., 9 to 10 atm.) is introduced as heated and pressurized by a compressor.
In this circumstances, there is a problem that the high pressure of refrigerant opens between the fin-tubes group 118 and the headers 120 which are bonded through thermal fusion and thus refrigerant leaks through openings formed as above.
Furthermore, when refrigerant leaks from the heat exchanger 112 as above, it is impossible to maintain the refrigerant pressure within the condenser 112 in a set cooling cycle or the refrigerant pressure of the entire cooling cycle. As the refrigerant pressure is decreased as above, the refrigerator fails to properly perform the cooling cycle while the discharged quantity of refrigerant may not correspond to the set temperature of the refrigerator.